c++ - Returning a new instance of a class -

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• how “return object” in c++? 7 answers

i thinking semantics of returning class type.

consider simple vector class.

#ifndef __vector_h__ #define __vector_h__  #include <cmath>  class vector2f {  public:     float x;     float y;      vector2f() : x(0), y(0) {}     vector2f(int x,int y) : x((float)x), y((float)y) {}     vector2f(float x, float y) : x(x), y(y) {}      ~vector2f() {}     float length() { return pow( float(x*x + y*y) , 0.5 ); }      void unit() {         //instead of making current vector unit vector         //i return unit vector         float len = length();         if(len != 1.0) {             x = x / len;             y = y / len;         }         return;     }   };   #endif 

the function unit() makes current vector unit vector, thinking instead return unit vector new unit vector (i may not want lose old 1 instance).

i started thinking becomes memory management nightmare because anytime unit() called, allocate memory , later have deleted. seems dumb way it.

vector2f unit() {     float len = length();     return new vector2f(x/len,y/len); } 

is there better way this? considered maybe having function demand reference vector2f object.

the payload vector2f decidedly small: 2 x float members. it's not worth allocating them on heap. instead consider capturing type reference or const reference function parameters , returning value.

the unit function be:

vector2f unit() {   float len = length();   return vector2f(x/len,y/len); }